This invention relates to a solid rigid restraining device bonded to a diaphragm to control the compression exerted upon the diaphragm.
The diaphragm of this invention is commonly used with weir type diaphragm valves, although other usage employing diaphragms are not precluded. Weir type diaphragm valves are particularly suited for processing high purity fluids used in the pharmaceutical, biotechnical, chemical, food and semiconductor industries. This is due to the exceptional ability of weir type valves to resist damage from the action of the fluids because only the diaphragm comes in contact with the fluid while the other parts of the valve are isolated unless the diaphragm is ruptured. However, weir type diaphragm valves experience a major drawback in that diaphragms require periodic replacement, whose cost and maintenance have to be figured in or budgeted. The diaphragm is sandwiched between the bonnet and the valve body of a diaphragm valve which are joined to each other by fasteners. Because the diaphragm is made of a flexible material, it offers minimal resistance to the force exerted in tightening the fasteners. Further, a user, in his/her desire to ensure closure of the resulting chamber between the bonnet and the valve body, has a tendency to overtighten the fasteners to prevent leakage of the fluid from the chamber. Due to this, diaphragms either deform or rupture, causing the frequent replacement.
The above problem is encountered during the assembly of the diaphragm valve. This should be differentiated from deformation and rupture of the diaphragm that are caused by the excessive force applied on the diaphragm during the actual usage of the valve, when the bottom surface of the diaphragm is compressed on the top surface of a weir, which movements prevent the flow of the liquid to and from the chamber. This latter problem is addressed by Fritz Muller in U.S. Pat. No. 5,377,956 which proposes the installation of an additional screw nut to limit the movement of the valve stem, which drives a compressor device that pushes the diaphragm to the surface of the weir. In U.S. Pat. No. 3,250,511, this problem is addressed by incorporating a detachable retainer ring clamped between the valve bonnet and the valve body which establishes a positive stop for the compressor device, referred to therein as the actuator. Other means such as the use of a backing sheet of a yieldable polymeric material or a metallic diaphragm internally bonded with the elastomeric diaphragm to form a composite two layered diaphragm were also proposed to solve the same problems which are encountered during the actual operation of the diaphragm valve.
None of the above means address the prevention of excessive force imposed upon the diaphragm during the fastening of the valve body with the bonnet connected to a diaphragm which is the main aspect addressed by the claimed invention. U.S. Pat. No. 3,628,770 proposes the use of a plate member intermediate between the bonnet and the diaphragm with a central opening defined by a rigid outwardly flared edge to protect the surface of the diaphragm from the sharp corners, burrs or irregularities on the bonnet which can damage the diaphragm while allowing the free flexing of the diaphragm as it closes and opens to control the flow of the fluid. While this invention also addresses the problem encountered during the actual operation of the diaphragm valve, it can to some extent, also minimize the compression on the diaphragm during its assembly. The device, however, requires a mechanical modification on the design and construction of a diaphragm valve amounting to purchasing and replacing the diaphragm valves currently in use. Further, since the flexible material making up the diaphragm is still in direct contact with the valve body, although shielded from the bonnet, there is still a possibility to overcompress the diaphragm sandwiched between these components.
The claimed invention, on the other hand, prevents excessive compression of the diaphragm and by directing the modification only at the construction of the diaphragm, it can be used with all existing varieties of diaphragm valves.
It is an object of this invention to provide a diaphragm having a bonded solid rigid material, referred to as compression restrainer, on an area adjacent to fasteners connecting the bonnet and the valve body together, to prevent overcompression of the periphery of the diaphragm during the assembly of a diaphragm valve.
It is also an object of this invention to provide a diaphragm with a compression restrainer that can be applied to any diaphragm valve thereby allowing the use of enlisting diaphragm valves.
It is a further object of this invention to provide a diaphragm with the compression restrainer that is inexpensive and whose usage significantly reduces the necessity for frequent replacement of the diaphragms.
It is still a further object of this invention to provide a diaphragm that can prevent loosening of the interconnection of the parts of a diaphragm valve during its actual operation.